Question Problem with connecting monitor

Feb 25, 2020
Firstly apologies but I am not very tech savvy so I hope I can get some help with this.

I have an old Dell laptop XPSL502 and prefer to use this than my newer laptop. I work a lot with graphic design so I bought a large dell monitor to be able to see things a bit clearer. When I connect the laptop to the monitor via a HDMI cable it works fine for a while then randomly the screen will suddenly change to a block colour and a loud buzzing noise comes from the laptop. Unfortunately I then have to restart the laptop so if I forget to save any work beforehand it is lost. I have connected my newer laptop to the monitor and all is fine and yes I could use the newer one but if I am honest I just prefer my old windows 7! Does anyone know why this happens and is there a fix for it?
1st, backup important/personal data of your laptop, like pictures, work,...

eventually it´s a driver or overheating problem

update all drivers of the laptop from the Dell homepage
eventually update the BIOS of it (don´t use the monitor while updating the BIOS)

check the temperature with the tool like GPU-Z (sensors) for the graphics unit and coretemp for the processor.